Ta— and Ta—N-based mixed system layers for use in Si microelectronics are currently being produced by plasma-based deposition processes (physical vapour deposition, PVD). With regard to the extreme demands for ever more highly integrated circuits, for example conformal layer deposition on structured surfaces, PVD processes are increasingly meeting the limits of practical achievability. For these applications, chemical vapour depositions (CVDs) down to atom layer-specific deposition with a special CVD process, known as atomic layer deposition (ALD), are increasingly being used. For these CVD processes, corresponding chemical starting materials of the individual elements for the particular desired layers must of course be available.
At the present time, for the CVD Ta-based layer structures, predominantly halides are being used, for example TaCl5, TaBr5; see WO 2000065123 A1, A. E. Kaloyeros et al., J. Electrochem. Soc. 146 (1999), p. 170-176, or K. Hieber, Thin Solid Films 24 (1974), p. 157-164. This is afflicted with various disadvantages. One is that halogen radicals are in many cases undesired for the formation of complex layer structures owing to their etching/corrosive properties, and another is that the tantalum halides have disadvantages as a result of their low volatility and the difficulty of processing them, being high-melting solids. Simple tantalum(V) amides, for example Ta(N(CH3)2)5, are likewise proposed; see, for example, Fix et al., Chem. Mater., 5 (1993), p. 614-619. With the simple amides, it is, however, usually possible to establish only particular decomposition ratios of Ta to N, which complicate exact control of the individual element concentrations in the layers. In many cases, Ta—V nitride films form (see, for example, Fix et al.: Ta3N5) and not the desired electrically conductive Ta(III) nitride layers (TaN). In addition, the films produced with these starting materials very often exhibit high, undesired concentrations of carbon. Tsai et al., Appl. Phys. Lett. 67(8), (1995); p. 1128-1130 therefore proposed t-BuN═Ta(NEt2)3 in TaN-CVD at 600° C. Owing to its relatively low volatility, this compound requires a high plant temperature and is therefore not very compatible with the typical production processes of integrated circuits. Other, similar tantalum amide imides have also been proposed; see, for example, Chiu et al., J. Mat. Sci. Lett. 11 (1992), p. 96-98, but these produced high carbon contents in the tantalum nitride layers without any further reactive gas. Recently, further tantalum nitride precursors have been proposed, for example by Bleau et al., Polyhedron 24(3), (2005), p. 463-468, which, owing to their complexity and complicated preparation, have disadvantages from the outset, or specific cyclopentadienyl compounds which either lead inevitably to TaSiN (not tantalum nitride) or require an additional nitrogen source not specified in detail (Kamepalli et al., US Pat. Appl. Publ. 2004142555 A1, Prior. Jan. 16, 2003, ATMI, Inc.). U.S. Pat. No. 6,593,484 (Kojundo Chemicals Laboratory Co., Ltd., Japan) proposes a suitable specific tantalum amide imide, but the synthesis proposed is difficult and poorly reproducible. R. Fischer et al. describe, in Dalton Trans. 2006, 121-128, mixed hydrazido-amido/imido complexes of tantalum, hafnium and zirconium and their suitability in CVD, but without any statement with regard to the Ta:N ratio in the resulting deposition product. J. Chem. Soc. Dalton Trans. 1990, 1087-1091 describes a trichlorobis(trimethylhydrazido complex), but there is no indication to its use in CVD.
These statements apply essentially or mutatis mutandis also to the analogous niobium compounds and the corresponding CVD chemistry.